As one who has taken more checkrides than I can remember, here's my advice:
-You're obviously ready or your CFI wouldn't have signed you off for it. Relax!
-Most DPE's take great joy in awarding someone their new PPL. Nobody likes to be the bearer of bad news. They want to see you do well and they're in your corner! So, Relax! I use to get a bigger kick out of seeing my students pass than they did. That big grin on their face, that you couldn't wipe off, was priceless!
-Nobody! And I mean, Nobody flies the perfect checkride. Not even that examiner sitting next to you. We, as humans, all make mistakes. Try hard not to make any and try not to make BIG ones but don't beat yourself up thinking about it the entire checkride if you do. That'll just about guarantee to distract you enough to make another one. Relax!
-Most important! I use to tell this to all my checkride applicants from PPL to type rides in the B757 or A300. The night before your ride find a quiet distraction such as taking in a good movie and/or dinner. Get to bed early, and try to get some sleep. A good nights sleep does wonders for memory and motor skills. Drink a lot of water to keep you hydrated and alert.
-Above all, RELAX! Remember, this was suppose to be FUN, right? If you mess up, what's the worse thing? You come back and do it again. Doesn't make you a bad pilot. I've seen excellent aviators have bad days and have to redo checkrides. I had to redo my initial CFI (said I didn't talk enough..I'm usually quiet by nature
)and F/E rides( missed a fuel valve problem which cause a fuel imbalance). Came back and passed each just fine the second time around.
-RELAX!!!!!!!!! Have fun!!!!!